1. Field of the Invention
The present invention relates to an article recognizing system which is used to automatically manage and exchange tools of a machine tool, to manage parts and products in a factory, to identify articles in a physical distribution system and the like.
2. Description of Prior Art
In general, in order to mechanize the automatic exchange or management of tools of a machine tool, discrimination of parts and products on an assembly conveying line in a factory, or the like, a system to recognize and manage the articles such as tools, parts, products and the like is necessary. To satisfy this demand, an article recognizing system has recently been developed. This system comprises a write/read control unit and a head connected thereto. The write/read control unit is connected to an upper (superior or host) control apparatus including computer system. On the other hand, an ID unit having therein a non-volatile memory to store ID data or the like of an article is attached to the articles which are sent on, e.g. a conveying line. When an article arrives at the position of the head, data is written into or read out from the ID unit by the head in a contactless manner under control of the write/read control unit in response to a command from the upper control apparatus.
Since the data transmission and reception are executed between the head of the write/read control unit and the ID unit in a contactless manner, if the distance between the head and the ID unit is improper, such a situation that data cannot be accurately written or read out may occur. Therefore, upon istallation, the adjustment of the distance between the head and the ID unit and the positioning thereof become important, and the severe adjusting work is required. On the other hand, after the positioning adjustment has once been performed, there occurs a case where the distance at which data can be stably written or read out changes due to the noises, circumstances or the like, so that a readjustment is required.
However, the conventional article recognizing system does not have a stable operation indicator to indicate that the data writing/reading operations can be correctly performed. Therefore, it is difficult to stably confirm the writing/reading operating range. Further, since the writing/reading operations for the ID unit are executed in response to a command from the upper control apparatus, upon adjustment in a field where the head is installed, the worker must go to the location where the upper control apparatus is installed and which is away from this field to operate the upper control apparatus. Thus, there are problems such that the adjusting work is difficult and it takes time. In addition, the write/read data cannot be checked or corrected in the field where the head is located.
In the article recognizing system, a plurality of write/read control units to be installed in the field are generally connected to one upper control apparatus.
The upper control apparatus is connected to a plurality of control units through transmission lines and gives write/read commands and the like to each of the write/read control units together with the unit number assigned thereto. If the command given from the upper control apparatus includes the self No., the write/read control unit recognizes this command and performs the data transmission and reception with the ID unit in accordance with this command.
The write/read control unit returns a response indicating that the command was correctly executed to the upper control apparatus together with the self No. after completion of the writing/reading operations. On the contrary, when the command could not be correctly finished, the write/read control unit returns an error code response indicative of the kind of error occurred to the upper control apparatus together with the self No. When the error code responses are returned, the upper control apparatus stores the error code data for every write/read control unit and manages the errors.
In such a conventional system, the error data generated are managed in a lump by the upper control apparatus. Therefore, when a plurality of write/read control units are connected to the upper control apparatus, there is a problem such that the load of the upper control apparatus increases to manage the errors generated.